Distortion indicator for radio receivers



16, 1940. J. H JONKER 2,197,341

DISTORTION INDICATOR'FOR RADIO RECEIVERS Filed Oct. 4, 1938 vvvvvv v1 INVENTOR J. L. H. JONKEK I bodiment thereof will now be described more drawing.

:Pa tented Apr. 16, 1940 UNITED STATES PATENT OFFICE 2,197,341 ms'ron'rroN INDICATOR ron aamo carve Johan Lodewijk Hendrik Junker, Eindhovem' Netherlands, assignor, by mesne assignments, to Radio Corporation of America, New York,

N. Y., a corporation 01' Delaware '4. 1938, Serial No. 233,166

March 11, 193

Applicatioll:l October 4 Claims. (01. 119-1) threshold value 'which is governed by the maximum admissible energy output of the set.

In order that the invention may be clearly understood and readily carried into efiect one emfully with reference to the accompanying Fig. 1 shows a wireless receiver l whose output energy is supplied to a loudspeaker 3 by way of a transformer 2. The low-frequency oscillations occurring across the primary of the output transformer 2 are fed to a rectifier 4 with threshold sensitiveness through a resistance 5 and a battery 6. The threshold sensitiveness is governed by a part of the battery 6 by which battery a positive bias is impressed on the cathode of the rectifier. When the amplitude of the low-frequency oscillations fed to the rectifier l-exceeds the threshold sensitiveness a potential loss occurs across the parallel resistance-capacity combination 8, 9 so that the negative voltage is supplied to the grid of the amplifier system of a cathoderay indicator 1. This results in such a potential variation across the resistance I'll in the anode circuit of the amplifier system that the raycontrol electrode II has imparted to it anincreasing positive voltage relatively to the cathode T the manner shown in Fig. 2, in which-only the I2 which results in an extension of that surface of the screen-shaped electrode l3 which is struck by electrons. The electrode I3 is coated with afterglowing fluorescent substance, preferably in cross-hatched parts have to be looked upon as coated with fluorescent material. So long as the amplitude of the low-frequency oscillations is lower than the threshold value the voltage-at the control electrode II is such that only thecumscribed in Fig. 2 by dotted lines. is struck by electrons simultaneously. Thus, in the event of overloading the cross-hatched parts which are struck become luminescent. Due to the fact that the fluorescent substance continues glowing for 5 a considerable length of time even instantaneous excessive loads are indicated in a distinct manner.

In the embodiment described the low-frequency voltages fed to the distortion indicator were ob-' tained from the output circuit of the final low- 10 frequency amplifier valve of the set. Voltages may also be obtained from the output circuit of one of the preceding amplifier valves; in this case the threshold sensitiveness of the distortion indicator has to be adjusted in, accordance II.

with the lower value of the voltages supphed thereto.

What I claim'is: 1. The combination with'a radio receiver, of

means for visually indicating distortion and oversignal in excess of a predetermined value, and-an as electron ray indicator tube having its grid controlled by said rectified voltage, the fluorescent screen of theindicator tube having the characteristic to glow for an appreciable time after electrons cease to impinge thereon whereby instantaneous overloads may be indicated.

2. Thecombination with a radio receiver, of means for visually indicating distortion and overload conditions of the receiver, comprising a circuit including a rectifier coupled to the receiver.

said circuit developing a rectified voltage therein which is proportional to the received signal in excess of a predetermined value, and an electron ray indicator tube having a cathode, a fluorescent anode surrounding the cathode and a ray-control electrode disposed in the electron stream between cathode and anode, means responsive to fluctuations in said rectified voltage for varying the direct current potential of the ray-control electrode and thereby varying the width of the electrical'shadow produced on the anode, the

. fluorescent anode of the tube having the characteristic that it persists in its fluorescence for an appreciable time after the flow of electrons thereto ceases whereby instantaneous overloads may be indicated.

3. The combination with a radio receiver, of means for visually indicating distortion and overload conditions thereof, comprising a. rectifier coupled to the receiver and arranged to draw 66 current when the signal voltage is in excess of a predetermined value, and an electron ray indicator tube having its grid controlled by the rectifled voltage, the indicating screen of said tube having fluorescent and non-fluorescent portions so arranged with respect to the control grid that only with grid voltages derived from the rectifier which are above the predetermined value will there be a visual indication of the overload con dition of the receiver,

4'. The combination with a radio receiver, of means for visually indicating distortion and overload conditions thereof, comprising a circuit ineluding a rectifier coupled to the receiver, said circuit developing a rectified voltage therein that with grid voltages derived from the rectifier which are below the predetermined value the electrons impinge upon the non-fluorescent por tion of the tube and with grid voltages above said value the electrons impinge upon the fluorescent portion to produce a visual indication of the overload condition of the receiver.

J OHAN LODEWIJ K HENDRIK J ONKER. 

